1. Field of the Invention
The present invention relates to a patient positioning device for use with a medical panorama X-ray photographing apparatus, for coinciding a subject portion of a patient to be examined with a tomographic zone of X-ray tomographing apparatus.
2. Prior Art
It is understood that to take a panoramic X-ray picture of high precision with the use of a medical panorama X-ray photographing apparatus, the coincidence of a portion of the patient to be tomographed (referred to as a subject hereinafter) with the tomographic zone of X-ray tomographing apparatus (referred to as a tomographic zone hereinafter) must be greatly considered. In the prior art, the positioning of the tomographic zone to an appropriate position is made by displacing a patient holding means or tomograph forming assembly automatically or manually with the use of designating means such as gauge, bite-block, light beam, etc. Then, the resulting position is checked by the operator through his visual observation.
However, in such positioning with visual observation by an operator, it will likely cause error resulting from visual error such as parallax. Particularly in the dental field, such positioning is commonly made in relation to a position of the front teeth of patient. In this case, it is very difficult to coincide the front teeth with a tomographic zone because the tomographic zone adapted to the front teeth has a depth of only a few mm. Thus substantially high skill and experience is required for the above coincidence.
Additionally, if the positioning is incomplete, the quality of an X-ray photograph will be lessened, thus resulting, at the worst, in extra irradiation of the patient since rephotographing is needed. Thereby, a simple and effective method of positioning has much been desired to be introduced.